Solar power has long been considered an attractive source of power since it is renewable and nonpolluting. In this regard, a number of systems have been developed to extract power from solar energy. Photovoltaic devices directly convert absorbed light into electrical energy. These devices are generally quite expensive, which restricts their use to specialized applications and precludes employing them in large-scale power generation systems. Furthermore, photovoltaic devices can only access a small portion of the available solar spectrum. Solar-thermal devices utilize the heating effect of solar radiation to produce power. Such devices are quite attractive since they can access virtually all of the solar spectrum. In solar-thermal devices, absorbed light is converted to heat, and the heat energy is employed directly, as for example to heat water, or it is employed to power engines, generators and the like.
In one group of solar-thermal generators, the heating effect of solar radiation is utilized to warm a gas, typically air, so as to cause that gas to rise. Devices of this type are shown in U.S. Pat. Nos. 4,275,304; 3,936,652; 4,016,725 and 5,300,817. Energy can be tapped from the system by disposing a turbine in the stream of rising air. One embodiment of this type of generator which has been proposed is referred to as a “solar chimney.” In devices of this type, a relatively large volume of air or other such working gas is trapped beneath an optically transparent surface where it is warmed by the absorption of solar radiation. The heated gas is allowed to rise through a relatively large chimney, and a turbine generator assembly disposed in the chimney is turned by the stream of rising gas. Generators of this type will be very difficult to build and maintain, since they require covering a very large area with glazing panels, and since chimney assemblies are expected to be one kilometer high. Such devices will be difficult to maintain, and can constitute an eyesore.
The present invention, as will be described in detail hereinbelow, constitutes a solar-thermal powered generator which does not require the use of any chimney assembly, nor does it require covering large areas with glazing panels. The generator assembly of the present invention may be built at a relatively low cost utilizing low-cost materials and relatively simple building techniques.